ML20008F989
| ML20008F989 | |
| Person / Time | |
|---|---|
| Site: | Allens Creek File:Houston Lighting and Power Company icon.png |
| Issue date: | 05/11/1981 |
| From: | Litton F Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20008F949 | List: |
| References | |
| NUDOCS 8105120454 | |
| Download: ML20008F989 (6) | |
Text
$
05/11/81 1
O UtilTio STATiS OF AMERICA 140 CLEAR NEGutATOU CO:ti!SSIO 1 BEFORE THE AT0l11C SAFETY AND LICENSING BOARD 1.4 :ne liattar of
)
)
ri]U3TJi LI11TI:iG A;i] POL'ER C0.1PANY )
Docket tio. 50-455 '
)
(.11 ens Creak fixlear Generating
)
Station, Unit 1)
)
f1RC STAFF SUPPt.EE: ITAL TESTIM 3 iY OF FELIX B. LITTON REGl.RDING TURBIfiE MISSILES
[Doherty Contention 47]-
Q.
Please state yoJr name and position with the NRC.
A.
fiy name is Felix B. Litton.
I am a Senior Materials Engineer with the Materials Engineering Branch of the Division of Engineering. A copy of
,ay stateaent of professional qualifications is attached.
Q.
Wnst is the purpose of this testinony?
A.
Tne purpose of this testimony is to respond to Doherty Conte 7 tion 47 which basically asserts that turbine nissiles cay'daaaga critical co'iponents of the Allens Creek plant (ACNGS). A complete statenent of the contention is set forth below.
Intervenor contends Applicant's nain generator turbine is not designed sufficiently to prevent turbine missiles fro:n danaging critical conponents of the systen.
Further, that stoppage or vibration of tne turbine following nissile tnrust will create dangerous nalting and damage to the turbine and nain stean power train of tne plant.
That one turbine has indeed expelled a portion of a turbine disk is shown by Board Notification BN 80-8. which cites a prelininary report of a portion
-8105120 $k
O r i
of a disc hurled during turbine synchronization at 1,800 rpa on February.14, '1980, at the Yankee Rowe nuclear plant in Massachusetts.
Cracking of turbine disks is the subject of Board Notification BN 80-4, which indicates "tne. cracking nay be more widespread than previously reported" and that one manufacturer, Westinghouse, is "[i]n the process of elevating some of their previously estinated turbine missile energies."
(BN 80-4, January 16, 1980.) The largest cracks detected to date ware found at Zion Station, Unit 1, and reported by tha Inspection & Enforcenent Division of the NRC on November 20, 1979.
Further, on March 11, 1980, special inspections were ordered for ten nuclear reactors of.their turbines.
Because of uncertainty of these calculations of missile energy and the dangers of missiles, to the functioning of. the ACNGS and consequent risk to this Intervenor's health and environnental interests, he urges admission of this contention to the proceedings.
Q.
Has the Staff evaluated the potential for damage due to turbine failure at ACNGS?
A.
Yes.
The potential for danage to safety related structures and components due to turbine failure has been evaluated by the Staff to determine the validity of the contention and to determine whether additional protection, beyond that inherently provided by building-orientation and the structural stability of the turbine, need be provided to further reduce the probabili1y of unacceptable danage to a safety related structure or components front the generation of missiles resulting fran the failure of the main generator turbine.
Q.
What was the Staff's conclusion?
A.
In the Safety Evaluation Report, Supp. No. 2, NOREG-0515, dated i
March 1979, the Staff concluded that the turbine generator is in a peninsular orientation relative to the reacter containment, auxiliary, and control buildings at the Allens Creek Nuclear Generating Station, 4
y
, ~.
i%_. --,..,, -
p
,,.,--,r_
_,,-_.,y-c.-=._m,-
.y w
e,--.
6 +
Unit 1, and complies with the guidelines of Regulatory Guide 1.115,
" Protection Against Low-Trajectory Turbine Elissiles." Our analysis indicates that the probability of striking the radwaste building, the only safety related structure within the low trajectory turbine missile strike zone, penetrating the building wall, and causing a significant release of airborne radioactive contamination is below 10'7 par year.
Q.
Who is the manufacturer and the type of main gcna.ator turbine to be placed at AC! LGS?
A.
The main generator turbine for the Allens Creek facility is manufactured by t ' General Electric Company. The turbine is a tandem-compound L
- , Type TC6F, with last-stage buckets 38 inches in length, operating at 1800 rpm. Modern turbine wheels manufactured by General Electric Company are made from vacuum poured NiCrMoV alloy forgings, which are heat treated to obtain the optinum desired strength, ductility and toughness. The chemical composition and strength level of turbine wheel forgings are chosen to best meet the service requirements of the wheel.
To optimize stress corrosion resistance, physical j
properties are maintained at the lowest level sufficient to adequately withstand operating stress and maintain structural integrity.
Optimized material chemistry and process conditions are chosen in order to produce sheel material possessing superior toughness properties and resistance to fracture.
Q.
What causes the potential for turbine failure?
A.
In the bore region of shrunk-on wheels, induced stresses result froa the interference between the wheel and shaft, and the centrifugal forces of the bucket and wheel.
Centrifugal stresses have been minimized c
4-in the General Electric turbines by optimizing the i; eel shape and nounting one row of backets on each wheel.
Reducing the centrifugal stresses lowers the nagnitude of the shaft-to-wheel interference necessary to nointain shrink at noraal operating speed. Thermal stresses induced by steady state and transient steam conditions are generally snall in comparison with shrink and centrifugal stresses.
Q.
What are the controls and tests utilized to assure quality standards?
A.
!1odern wheels manufactured for nuclear turbines are made from the highest quality NiCrltoV alloy forgings. During aanufacture, the wheels must pass stringent material acceptance standards.
In addition to a CoGplete visual and magnetic particle eXauination of all bore and external surfaces, the wheel forgings are subjected to 100% volumetric ultrasonic examination at the time of nanufacture. Nuclear turbine wheels are spin tested to 20% overspeed to further assure the integrity of the wheel and to ninimize the probability of an undetected crack or flaw of critical size, which could lead to spontaneous propagation at normal operating speeds when the turbine wheels are placed in service.
Q.
What is the operating experience of turbine units manufactured i
by General Electric Company?
A.
The service experience with the forty-two main generator turbine units nanufactured by General Electric Company and operated in nuclear power facilities has been excellent. The 1579 wheels operating in these i
I units have accumulated over 9,000 wheel years of service without failure.
To date, a substantial portion of these wheels have received an in-service inspection procedure without finding a single crack-like
indication, although water cutting has been identified in the disk keyway.
The General Electric Company has developed an ultrasonic inspection procedure for the critical bore and keyway regions which can be perforned
-on the wheels without disassembly of the turbine. The General Electric Company recommends the inspection procedure for the nuclear turbine wheels in conjunction with steari purity to significantly reduce the probability of a wheel burst and the subsequent generation of missiles.
Q.
What is the Staff conclusion with respect to this contention?
A.
The Staff concludes that there is a low probability of failure of the main generator turbine with the generation of uissiles resulting in unacceptable dauage to the safety related structures and components at the Allens Creek fluclear Generating Station, Unit 1.
Our conclusion is based on the fact that the main generator turbine is in a peninsular orientation with respect to the reactor containment and other safety related buildings, the quality assurance imposed on the materials used in the construction of the turbine, and the 16 service inspection procedures reconnended by the General Electric Company to assure inservice integrity of the main generator turbine.
PROFESSIONAL QUALIFICATIONS FELIX B. LITTON I am a Senior Materials Engineer in the Materials Engineering Branch of the Office of Nuclear Reactor Regulation, Nuclear Regulatory Commission.
I am assigned to the Inservice Inspection and Component Integrity Sections and my duties involve the review and evaluation of materials and processes used in the construction and operation of. components in the nuclear power indus try.
My education consists of a B. S. (1936) and M. S. (1937) degree in Physical Chenistry from Virginia Polytechnic Institute, Blackstaro, Va.
I have completed additional study in Material Science at the Univs.sity of New Mexico and have taken special courses in Fracture Mechanics and other job oriented courses at Union College and Georce b'ashington University.
Prior to joining the Nuclear Regulatory Commission, my experience consists of metallurgical research related to the preparation, fabrication and alloy formation of new structural raterials for nuclear, advanced aircraft and high temperature application.
I have published in technical journals on the environmental behavior, thermodynamic stability and mechanical oroperties of uranium, plutonium, vanadium, zirconium, tetanium, hafrium and silicon and their alloys. Although my orimary experience in ferrous metallurgy has related to the cause of material failure in service, I have managed metallurgic.
research on welding and welding processes.
e
-